Optical fiber sensor and measuring system using the same

Abstract

The present invention is the optical fiber sensor, that laser pulses from a laser source are separated into a reference path and a measurement path by the second optical coupler via the first optical coupler, the first FRM is provided at an end of the reference path, the second FRM is provided at an end of the measurement path, and the reference reflected light of the first FRM and the measurement reflected light of the second FRM are interfered at the second optical coupler and are converted into three phases. The first phase pulses are transmitted to the optical synthesis section via the first optical coupler, second phase pulses are transmitted to the optical synthesis section via the first delay section, and third phase pulses are transmitted to the optical synthesis section via the second delay section. The time division pulse train is outputted from the optical synthesis section.

1 . An optical fiber sensor,
 wherein laser pulses from a laser source are separated into two phases of a reference path and a measurement path including a measuring object, which form an interferometer, by a second optical coupler via a first optical coupler;   wherein a first Faraday Rotator Mirror (FRM) is provided at an end of said reference path, and a second FRM is provided at an end of said measurement path; and   wherein a reference reflected light of said first FRM and a measurement reflected light of said second FRM are interfered at said second optical coupler and are converted into three phases, converted first phase pulses are transmitted to an optical synthesis section via said first optical coupler, converted second phase pulses are transmitted to said optical synthesis section via a first delay section, converted third phase pulses are transmitted to said optical synthesis section via a second delay section, and a time division pulse train is outputted from said optical synthesis section.   
     
     
         2 . The optical fiber sensor according to  claim 1 , wherein all transmissions of said laser pulses are performed by using a single mode (SM) fiber. 
     
     
         3 . The optical fiber sensor according to  claim 1 , wherein a delay time of said second delay section is longer than a delay time of said first delay section. 
     
     
         4 . A measuring system to measure a displacement of said measuring object by measuring a peak value of said time division pulse train as claimed in  claim 1 . 
     
     
         5 . An optical fiber sensor,
 wherein laser pulses from a laser source are transmitted to a second Polarization Maintaining (PM) optical coupler by a first PM fiber via a polarizer and a first PM optical coupler;   wherein said laser pulses are separated into two phases of a reference path and a measurement path including a measuring object, which form an interferometer, at said second PM optical coupler and are transmitted by a second PM optical fiber;   wherein a first mirror is provided at an end of said reference path, and a second mirror is provided at an end of said measurement path;   wherein a reference reflected light of said first mirror and a measurement reflected light of said second mirror are interfered at said second PM optical coupler and are converted into three phases;   wherein converted first phase pulses are outputted by a third PM fiber via said first PM optical coupler and is transmitted to an optical synthesis section by a first SM optical fiber being connected to said third PM fiber;   wherein converted second phase pulses are outputted from said second PM optical coupler by a fourth PM fiber and is transmitted to said optical synthesis section, via a first delay section, by a second SM fiber being connected to said fourth PM fiber;   wherein converted third phase pulses are outputted from said second PM optical coupler by a fifth PM fiber and is transmitted to said optical synthesis section, via a second delay section, by a third SM fiber being connected to said fifth PM fiber; and   wherein a time division pulse train is outputted from said optical synthesis section.   
     
     
         6 . The optical fiber sensor according to  claim 5 , wherein a delay time of said second delay section is longer than a delay time of said first delay section. 
     
     
         7 . A measuring system to measure a displacement of said measuring object by measuring a peak value of said time division pulse train as claimed in  claim 5 . 
     
     
         8 . An optical fiber sensor that measuring pulses are transmitted to “n(≥2)” interferometers respectively including a measuring object, and Time Division Multiplexing (TDM) pulse trains corresponding to respective displacements of said measuring objects from said “n” interferometers are optically synthesized and are outputted,
 wherein “n−1” optical couplers to convert laser pulses into two phases of said measuring pulses and delaying pulses are provided; 
 wherein a first stage optical coupler inputs laser pulses from a laser source, and a second stage to (n−1)th stage optical couplers respectively input said delaying pulses from a previous stage via a delay section; 
 wherein n-th optical coupler transmits said delaying pulses from (n−1)th optical coupler to said n-th interferometer and inputs; and 
 wherein respective TDM pulse trains outputted from said “n” interferometers are sequentially and optically synthesized, and a multiple TDM pulse train is outputted. 
 
     
     
         9 . The optical fiber sensor according to  claim 8 ,
 wherein respective said “n” interferometers comprise a constitution that: said laser pulses are separated into two phases of a reference path and a measurement path including a measuring object, which form an interferometer, by a second optical coupler via a first optical coupler; a first Faraday Rotator Mirror (FRM) is provided at an end of said reference path and a second FRM is provided at an end of said measurement path; and a reference reflected light of said first FRM and a measurement reflected light of said second FRM are interfered at said second optical coupler and are converted into three phases, converted first phase pulses are transmitted to an optical synthesis section via said first optical coupler, converted second phase pulses are transmitted to said optical synthesis section via a first delay section, converted third phase pulses are transmitted to said optical synthesis section via a second delay section, and a time division pulse train is outputted from said optical synthesis section.   
     
     
         10 . The optical fiber sensor according to  claim 8 ,
 wherein respective said “n” interferometers comprise a constitution that: said laser pulses are transmitted to a second Polarization Maintaining (PM) optical coupler by a first PM fiber via a polarizer and a first PM optical coupler; said laser pulses are separated into two phases of a reference path and a measurement path including a measuring object, which form an interferometer, at said second PM optical coupler and are transmitted by a second PM optical fiber; a first mirror is provided at an end of said reference path and a second mirror is provided at an end of said measurement path; a reference reflected light of said first mirror and a measurement reflected light of said second mirror are interfered at said second PM optical coupler and are converted into three phases; converted first phase pulses are outputted by a third PM fiber via said first PM optical coupler and is transmitted to an optical synthesis section by a first SM optical fiber being connected to said third PM fiber; converted second phase pulses are outputted from said second PM optical coupler by a fourth PM fiber and is transmitted to said optical synthesis section, via a first delay section, by a second SM optical fiber being connected to said fourth PM fiber; converted third phase pulses are outputted from said second PM optical coupler by a fifth PM fiber and is transmitted to said optical synthesis section, via a second delay section, by a third SM fiber being connected to said fifth PM fiber; and a time division pulse train is outputted from said optical synthesis section.   
     
     
         11 . A measuring system to measure respective displacements of said “n” measuring objects by measuring a peak value of said multiple TDM pulse train as claimed in  claim 8 . 
     
     
         12 . An optical fiber sensor,
 wherein laser pulses from a laser source are separated into two phases of a reference path and a measurement path including a measuring object, which form an interferometer, by a second optical coupler via a first optical coupler;   wherein a first mirror is provided at a junction tip of said second optical coupler of said reference path, and a collimator lens is provided at a junction tip of said second optical coupler of said measurement path;   wherein a spatial coupling is formed by said second optical coupler and said measuring object, and a second mirror to reflect a measuring light is provided in said spatial coupling;   wherein laser pulses from said collimator lens are inputted to said measuring object via said spatial coupling, a signal light reflected on said second mirror is interferes with a reflected light of said first mirror, and interfered light is converted into three phases at said second optical coupler; and   wherein converted first phase pulses are transmitted to an optical synthesis section via said first optical coupler, converted second phase pulses are transmitted to said optical synthesis section via a first delay section, converted third phase pulses are transmitted to said optical synthesis section via a second delay section, and a time division pulse train is outputted from said optical synthesis section.   
     
     
         13 . An optical fiber sensor,
 wherein laser pulses from a laser source are separated into two phases of a reference path and a measurement path including a measuring object, which form an interferometer, by a second optical coupler via a first optical coupler;   wherein an end face mirror is provided at a junction tip of said second optical coupler of said reference path, and a collimator region is provided at a junction tip of said second optical coupler of said measurement path;   wherein a spatial coupling is formed by an input and output section of said second optical coupler and a prism mirror in said measuring object;   wherein laser pulses of said reference path are returned to said second optical coupler by reflecting at said end surface mirror, a laser pulse outputted from said collimator region are entered to said end surface mirror via said prism mirror in said spatial coupling, a signal light reflected on said end surface mirror is inputted to said collimator region via said prism mirror and is returned to said second optical coupler, and returned light is converted into three phases at said second optical coupler; and   wherein converted first phase pulses are transmitted to an optical synthesis section via said first optical coupler, converted second phase pulses are transmitted to said optical synthesis section via a first delay section, converted third phase pulses are transmitted to said optical synthesis section via a second delay section, and a time division pulse train is outputted from said optical synthesis section.   
     
     
         14 . A measuring system to measure a displacement of said measuring object by measuring a peak value of said time division pulse train as claimed in  claim 12 .